Connection of SHALLCROSS family with SMITH family in Philadelphia

Elizabeth SHALLCROSS Dunn (1869-1956) was the daughter of Thomas Dunn who lived in Delaware County, Pennsylvania. Her mother was Elizabeth SHALLCROSS Smith who was born in the Frankford section of Philadelphia (1841-1929). She married Thomas Dunn in Media, Pa in 1860.
Elizabeth Shallcross Dunn retained the name Shallcross when she married J.W.Lukens. (Elizabeth Shallcross Lukens). This would suggest that Shallcross was a family name.
Since the Shallcross family lived generally in the Frankford area as did the family of Elizabeth Shallcross Smith, there would seem to be a family connection. How did Elizabeth Shallcross Smith , born in Frankford, meet Thomas Dunn, Born in Edgemont, Pa. This is what I would like to determine. It is not likely that Thomas Dunn was ever in Frankford so I am guessing that the merging of families would have occurred near Media.